The next five years could bring another pounds 25bn of windfalls for consumers as more building societies and other mutual organisations follow the lead of the Halifax and convert to companies listed on the stock market. A leading City of London investment bank predicts that millions of people will share in this new bonanza, having already picked up a predicted pounds 35bn of free shares in converting institutions by the end of this year.

As well as the Halifax, several well-known building societies including the Woolwich have joined the stock market this year, along with Norwich Union, the life insurance company. About a quarter of the free shares members of former building societies have received so far in 1997 have been sold immediately.

The rush to the stock market has delighted carpetbaggers and fuelled the present consumer boom. But the give-away, expected to add more than pounds 4bn to consumer spending this year, has also helped trigger the four interest rate increases announced since 1 May.

According to a report from HSBC Markets, part of the group which owns Midland Bank, it would be premature to believe the bonanza is over, even though no conversions are so far scheduled for after this year. HSBC argues that the recent vote against abandoning mutual status by members of the Nationwide marked a rejection of the rebel candidates being put up for election to the board, rather than the idea of a payout on conversion to a bank, forecast to be in the region of pounds 7bn.

Flotations or takeovers amongst the remaining 70-plus mutual building societies, who are dominated by the Nationwide, could deliver windfall payouts of up to pounds 15bn in theory, the report says. It says it is reasonable to assume that half to two-thirds of this will be handed straight out to members as free shares.

Mutual insurance companies could deliver an even bigger bonanza, although some of the payout would take the form of payments into policyholders' funds rather than an immediate share handout.

In addition, other mutual organisations are candidates for shedding their collective ownership and parcelling out their assets to members, the bank suggests.

The most obvious example is the Co-operative Wholesale Society. Although a recent takeover bid failed ignominiously, others might think it worth trying to overturn the group's co-operative status.

Other examples include the London taxi firm Dial-a-Cab, whose 1,600 members would gain pounds 7,000 each from a stock market flotation which valued the company at pounds 10m. They paid just pounds 50 each to join.

Both of the two main motoring organisations, the AA and RAC, are also collectively owned by their members.

Even the Church is a mutual organisation, rich in assets, the report points out, although it does not suggest any candidates to mount a takeover bid.